1. Field of the Invention
The present invention relates to a method of charging a lithium ion secondary battery, a charging apparatus, and a power supply apparatus.
2. Related Background Art
Many lithium ion secondary batteries have been in use as batteries for driving devices such as cellular phones, notebook PCs, and PDAs, because of their high capacity, high energy density, excellent charging/discharging cycle characteristic, ability to keep a rated output for a long period, etc.
A constant current constant voltage (CCCV) scheme has usually been employed for charging a lithium ion secondary battery. In the constant current constant voltage scheme, the battery is initially charged to a predetermined upper limit voltage by a constant current, and then is held at this voltage. Since the current value decays in the constant voltage mode, the charging is terminated at the time when a predetermined current value is attained (see, for example, Japanese Patent Application Laid-Open No. HEI 5-111184).